This application is a Section 371 of International Application No. PCT/JP02/02159, filed Mar. 7, 2002, the disclosure of which is incorporated herein by reference.
The present invention relates to a vertical deflection apparatus comprising a correction circuit that corrects a north-south pincushion distortion on a CRT (Cathode-Ray Tube).
In a CRT, the distance from its deflecting center point to its screen (fluorescent screen) increases toward its periphery, so that the swing of an electron beam is the largest at four corners of the screen. Consequently, a north-south (upper-lower) pincushion distortion and an east-west (right-left) pincushion distortion are generated in an image displayed on the screen of the CRT. Particularly, the north-south pincushion distortion is referred to as an NS pincushion distortion, and the east-west horizontal pincushion distortion is referred to as an EW pincushion distortion. The larger the deflection angle of the electron beam is, the larger the pincushion distortions become.
FIG. 16(a) is a diagram showing an example of an NS pincushion distortion on a screen of a CRT, and FIG. 16(b) is a waveform diagram showing an NS pincushion distortion correction current superimposed on a vertical deflection current. In FIG. 16, H indicates a horizontal scanning period, and V indicates a vertical scanning period.
As shown in FIG. 16(a), the NS pincushion distortion on the screen of the CRT is in a shape which is constricted at its center, as compared with both its right and left ends. The NS pincushion distortion can be corrected by respectively moving the centers of horizontal scanning lines upward and downward, as indicated by arrows. Therefore, an NS pincushion distortion correction current (hereinafter abbreviated as a correction current) am which changes in a parabolic shape in the horizontal scanning period is superimposed on a sawtooth vertical deflection current VI which changes in the vertical scanning period, as shown in FIG. 16(b). The correction current am has a positive polarity in the first half of a vertical scanning interval (the upper half of the screen), and has a negative polarity in the latter half of the vertical scanning interval (the lower half of the screen). The amplitude of the correction current am increases toward upper and lower ends of the screen from the center thereof.
In order to superimpose a correction current on a vertical deflection current, a system using a supersaturated reactor and a transformer system in which a transformer is inserted in series with a vertical deflection coil and is driven by a parabolic current having a horizontal scanning period (hereinafter referred to as a horizontal parabolic current) have been conventionally employed.
FIG. 17 is a schematic view showing the correction of an NS pincushion distortion by the conventional supersaturated reactor system, where FIG. 17(a) is a diagram showing a supersaturated reactor, and FIG. 17(b) is a diagram showing the relationship between a magnetic flux density B and a magnetic field H in the supersaturated reactor.
In FIG. 17(a), a core 50 in the supersaturated reactor has three legs. Further, a core 51 is arranged on the core 50, and a permanent magnet 52 is arranged on the core 51. A horizontal deflection current HI is caused to flow through windings LH1 and LH2 of the legs on both sides of the core 50. Consequently, a magnetic flux "PHgr"H is generated. A vertical deflection current VI is caused to flow through a winding LV of the leg at the center of the core 50. Consequently, a magnetic flux "PHgr"V is generated. Further, a magnetic flux "PHgr"B is generated by the permanent magnet 52. In the supersaturated reactor, when the magnetic field H is strengthened, the magnetic flux density B is saturated, as shown in FIG. 17(b).
By the configuration shown in FIG. 17(a), the correction current am is superimposed on the vertical deflection current VI supplied to the vertical deflection coil, as shown in FIG. 16(b). Also in the transformer system, the same control is carried out. In such a way, the NS pincushion distortion is corrected.
A horizontal deflection coil and a vertical deflection coil are arranged so as to be orthogonal inside a deflection yoke. From a problem in the fabrication of the deflection yoke, orthogonality between the horizontal deflection coil and the vertical deflection coil is not necessarily ensured. Accordingly, a current component caused by a horizontal deflection current is induced by electromagnetic coupling from the horizontal deflection coil to the vertical deflection coil inside the deflection yoke.
Furthermore, a horizontal flyback pulse generated in the horizontal deflection coil in a horizontal blanking interval reaches a voltage of a thousand and several hundred Vp-p (volt peak-to-peak), and a harmonic component of the horizontal flyback pulse has a frequency which is several ten times the horizontal scanning frequency. Accordingly, the horizontal deflection coil and the vertical deflection coil are coupled to each other through a stray capacitance between the horizontal deflection coil and the vertical deflection coil. Consequently, a current component caused by the horizontal deflection current is induced by electrostatic coupling from the horizontal deflection coil to the vertical deflection coil.
Induction of a current component from a horizontal deflection coil to a vertical deflection coil is referred to as HV crosstalk, and a current component induced from the horizontal deflection coil to the vertical deflection coil is referred to as an HV crosstalk component. When the HV crosstalk component is superimposed on a vertical deflection current supplied to the vertical deflection coil, scanning lines are distorted, so that an image to be displayed is distorted.
A current component caused by the vertical deflection current is induced from the vertical deflection coil to the horizontal deflection coil. However, the horizontal deflection current is as large as several ten Ap-p (ampere peak-to-peak), while the vertical deflection current is as small as 1 to 2 Ap-p. Further, a voltage of a pulse generated in the vertical deflection coil in a vertical blanking interval is less than 100 volts, and the frequency thereof is from several ten hertz to a maximum of several hundred hertz. Therefore, the current components respectively induced by electromagnetic coupling and electrostatic coupling from the vertical deflection coil to the horizontal deflection coil are so small that they are hardly worth consideration.
In the correction of the NS pincushion distortion using the conventional supersaturated reactor system and transformer system, the HV crosstalk generated inside the deflection yoke is not considered. FIG. 18 is a diagram for explaining the HV crosstalk.
FIG. 18(a) illustrates a vertical deflection current VI on which a correction current is superimposed, FIG. 18(b) illustrates a correction current am, FIG. 18(c) illustrates an HV crosstalk component CR, and FIG. 18(d) illustrates a synthesized waveform of the correction current am and the HV crosstalk component CR. In FIG. 18(a), the correction current am superimposed on the vertical deflection current VI is roughly illustrated. In FIG. 18, V indicates a vertical scanning period.
As shown in FIG. 18(a), a correction current, which changes in a parabolic shape in a horizontal scanning period, is superimposed on the sawtooth vertical deflection current VI, which changes in the vertical scanning period, in order to correct an NS pincushion distortion. The polarity of the correction current am is reversed in the upper half and the lower half of a screen of a CRT, as described above. Consequently, the correction current am superimposed on the vertical deflection current VI differs in polarity in the upper half and the lower half of the vertical deflection current VI, as shown in FIG. 18(b).
As shown in FIG. 18(c), the HV crosstalk component CR which periodically changes in a horizontal scanning periods within a vertical scanning interval is generated from a horizontal deflection coil to a vertical deflection coil. The polarity of the HC crosstalk component CR is the same within the vertical scanning interval.
When the HV crosstalk component CR is synthesized with the correction current am, as shown in FIG. 18(d), therefore, the peak of the correction current am in the first half of the vertical scanning interval is shifted to the left, and the peak of the correction current in the latter half thereof is shifted to the right. Consequently, a distortion in an image which differs in the upper half and the lower half of the screen of the CRT is generated.
Furthermore, an NS pincushion distortion generated by a combination of the deflection yoke and the CRT is ideally symmetrical. However, the NS pincushion distortion may not, in some cases, be symmetrical due to various variations in characteristics. Consequently, transverse lines may not, in some cases, be displayed straight on the screen of the CRT.
FIG. 19 is a conceptual diagram for explaining the correction of an NS pincushion distortion, where FIG. 19(a) illustrates an NS pincushion distortion at the time of uncorrection on a screen of a CRT, FIG. 19(b) illustrates a correction waveform, and FIG. 19(c) illustrates the screen of the CRT at the time of correction.
When the NS pincushion distortion shown in FIG. 19(a) is corrected using the parabolic correction waveform shown in FIG. 19(b), the NS pincushion distortion can be corrected in a linear shape, as shown in FIG. 19(c).
Meanwhile, a request to flatten the CRT is being strengthened by being affected by a recent FPD (Flat Panel Display) represented by an LCD (Liquid Crystal Display) and a PDP (Plasma Display Panel).
When the CRT is flattened, however, an NS pincushion distortion and an EW pincushion distortion are increased. The shape of the pincushion distortion on the CRT having a normal deflection angle exhibits parabolic waveform characteristics (second power (square) characteristics). However, a higher-order distortion component is generated in the pincushion distortion on the CRT having a large deflection angle such as the flattened CRT. Particularly with respect to the NS pincushion distortion, transverse lines in the horizontal direction are in a pincushion shape, causing a so-called gull-wing distortion which deviates from simple parabolic waveform characteristics (square characteristics).
FIG. 20 is a conceptual diagram for explaining the generation of a gull-wing distortion, where FIG. 20(a) illustrates an NS pincushion distortion at the time of uncorrection on a screen of a CRT, FIG. 20(b) illustrates a correction waveform, and FIG. 20(c) illustrates the screen of the CRT at the time of correction.
When the NS pincushion distortion shown in FIG. 20(a) is corrected using the parabolic correction waveform shown in FIG. 20(b), a gull-wing distortion having a high-order distortion component shown in FIG. 20(c) is generated.
FIG. 21 is a diagram showing a second power (square) waveform and a waveform having a higher-order distortion component in normalized manner. The gull-wing distortion is the difference, between the second power waveform shown in FIG. 21 and the waveform having a higher-order distortion component, generated as a distortion on the screen of the CRT.
When the deflection angle of the CRT is thus increased, the NS pincushion distortion cannot be corrected using a horizontal parabolic current having the second power (square) waveform.
A harmonic component of the horizontal parabolic current (a second power component) can be also added to a vertical deflection current. However, the inductance of a winding of the vertical deflection coil is on the order of several mH, and the resistance component of the winding of the vertical deflection coil is on the order of several ten ohms. Accordingly, the vertical deflection coil itself operates as a low-pass filter with respect to a component having a frequency which is not less than the horizontal scanning frequency. When it is considered that the harmonic component of the horizontal parabolic current is added, therefore, a harmonic component which is significantly larger than a basic horizontal parabolic current must be added to the vertical deflection current, thereby causing the necessity of widening the dynamic range of a circuit.
Furthermore, in the correction of the NS pincushion distortion using the conventional supersaturated reactor system, the horizontal parabolic current derived from of the horizontal deflection current is utilized. Accordingly, the horizontal parabolic current also flows in the vertical blanking interval, so that power consumption is high.
An object of the present invention is to provide a vertical deflection apparatus capable of sufficiently correcting a north-south pincushion distortion without being affected by crosstalk from a horizontal deflection coil to a vertical deflection coil.
Another object of the present invention is to provide a vertical deflection apparatus capable of sufficiently correcting an asymmetrical north-south pincushion distortion.
Still another object of the present invention is to provide a vertical deflection apparatus capable of sufficiently correcting a north-south pincushion distortion even when the deflection angle thereof is large.
A vertical deflection apparatus according to an aspect of the present invention is a vertical deflection apparatus for supplying a vertical deflection current to a vertical deflection coil to deflect an electron beam in the vertical direction of a screen, which comprises a vertical deflection current output circuit that outputs the vertical deflection current to the vertical deflection coil; a correction circuit that outputs a correction signal periodically changing in a parabolic shape in a horizontal scanning period to correct a north-south pincushion distortion; a modulation circuit that modulates the phase of the correction signal output from the correction circuit in a vertical scanning period; and a superimposition device that superimposes a correction current based on an output signal of the modulation circuit on the vertical deflection current.
In the vertical deflection apparatus according to the present invention, the vertical deflection current is output to the vertical deflection coil by the vertical deflection current output circuit. The correction signal changing in a parabolic shape in the horizontal scanning period is output to correct the north-south pincushion distortion by the correction circuit. Further, the phase of the correction signal output from the correction circuit is modulated in the vertical scanning period by the modulation circuit. The correction current based on the output signal of the modulation circuit is superimposed on the vertical deflection circuit by the superimposition device.
In this case, the phase of the correction signal is modulated in the vertical scanning period, so that the effect of a crosstalk component induced from a horizontal deflection coil to the vertical deflection coil is corrected. Consequently, the north-south pincushion distortion can be sufficiently corrected without being affected by crosstalk.
The modulation circuit may delay the phase of the correction signal in the first half of a vertical scanning interval, while advancing the phase of the correction signal in the latter half of the vertical scanning interval.
In this case, the crosstalk component is synthesized with the correction signal, whereby the phase of the correction signal is advanced in the first half of the vertical scanning interval, while being delayed in the latter half of the vertical scanning interval. Consequently, the effect of the crosstalk component can be corrected by delaying the phase of the correction signal in the first half of the vertical scanning interval, while advancing the phase of the correction signal in the latter half of the vertical scanning interval.
The correction circuit may have the function of shifting the phase at the peak of the correction signal from the middle of a horizontal scanning interval.
Consequently, an asymmetrical north-south pincushion distortion can be corrected without being affected by the crosstalk.
The correction circuit may comprise a folded waveform generator that generates a folded waveform changing in a sawtooth shape in the horizontal scanning period and having a bending point at a level which is half the amplitude thereof, a turn-up waveform generator that generates a turn-up waveform obtained by turning up a portion below the level which is half the amplitude thereof in the folded waveform generated by the folded waveform generator at the bending point, and a correction signal generator that generates the correction signal having a peak corresponding to a turn-up point of the turn-up waveform generated by the turn-up waveform generator.
In this case, the position at the peak of the correction signal can be adjusted by adjusting the position at the bending point of the folded waveform. Consequently, the phase at the peak of the correction signal can be shifted from the middle of the horizontal scanning interval.
The correction signal generator may generate the correction signal by raising the turn-up waveform to the n-th power, where the n may be a real number.
Consequently, the parabolic correction signal having the peak corresponding to the turn-up point is obtained. In this case, a higher-order distortion component generated in the north-south pincushion distortion can be corrected by adjusting the value of n. Even when the deflection angle is large, therefore, a gull-wing distortion is prevented from being generated without being affected by the crosstalk, thereby making it possible to sufficiently correct the north-south pincushion distortion.
The correction circuit may output the correction signal by a combination of a parabolic waveform changing in the horizontal scanning period and another function waveform.
In this case, the higher-order distortion component generated in the north-south pincushion distortion can be corrected by a combination of the parabolic waveform and another function waveform. Even when the deflection angle is large, therefore, the gull-wing distortion is prevented from being generated without being affected by the crosstalk, thereby making it possible to sufficiently correct the north-south pincushion distortion.
The vertical deflection apparatus may further comprise a plurality of pulse generation circuits that respectively generate pulse signals in the horizontal scanning period, and a synthesizer that synthesizes the pulse signals respectively generated by the plurality of pulse generation circuits with the correction signal output from the correction circuit. The superimposition device may superimpose a correction current based on an output signal of the synthesizer on the vertical deflection current.
In this case, a pulse component corresponding to the pulse signal in the correction current superimposed on the vertical deflection current is integrated by the vertical deflection coil. Consequently, the higher-order distortion component generated in the north-south pincushion distortion is corrected by the integrated pulse component. Even when the deflection angle is large, therefore, the gull-wing distortion is prevented from being generated without being affected by the crosstalk, thereby making it possible to sufficiently correct the north-south pincushion distortion.
The vertical deflection apparatus may further comprise a blanking circuit that sets the correction current to zero in a vertical blanking interval.
In this case, the correction current becomes zero in the vertical blanking interval, thereby achieving power saving.
A vertical deflection apparatus according to another aspect of the present invention is a vertical deflection apparatus for supplying a vertical deflection current to a vertical deflection coil to deflect an electron beam in the vertical direction of a screen, which comprises a vertical deflection current output circuit that outputs the vertical deflection current to the vertical deflection coil; a correction circuit that outputs a correction signal periodically changing in a parabolic shape in a horizontal scanning period to correct a north-south pincushion distortion; and a superimposition device that superimposes a correction current based on the correction signal output from the correction circuit on the vertical deflection current, the correction circuit having the function of shifting the phase at the peak of the correction signal from the middle of a horizontal scanning interval.
In the vertical deflection apparatus according to the present invention, the vertical deflection current is output to the vertical deflection coil by the vertical deflection current output circuit. The correction signal changing in a parabolic shape in the horizontal scanning period is output to correct the north-south pincushion distortion by the correction circuit. Further, the correction current based on the correction signal output from the correction circuit is superimposed on the vertical deflection current by the superimposition device.
In this case, the correction circuit has the function of shifting the phase at the peak of the correction signal from the middle of the horizontal scanning interval, thereby making it possible to sufficiently correct an asymmetrical north-south pincushion distortion.
The correction circuit may comprise a folded waveform generator that generates a folded waveform changing in a sawtooth shape in the horizontal scanning period and having a bending point at a level which is half the amplitude thereof, a turn-up waveform generator that generates a turn-up waveform obtained by turning up a portion below the level which is half the amplitude thereof in the folded waveform generated by the folded waveform generator at the bending point, and a correction signal generator that generates the correction signal having a peak corresponding to a turn-up point of the turn-up waveform generated by the turn-up waveform generator.
In this case, the position at the peak of the correction signal can be adjusted by adjusting the position at the bending point of the folded waveform. Consequently, the phase at the peak of the correction signal can be shifted from the middle of the horizontal scanning interval.
The correction signal generator may generate the correction signal by raising the turn-up waveform to the n-th power, where the n may be a real number.
Consequently, the parabolic correction signal having the peak corresponding to the turn-up point is obtained. In this case, a higher-order distortion component generated in the north-south pincushion distortion can be corrected by adjusting the value of n. Even when the deflection angle is large, therefore, a gull-wing distortion is prevented from being generated without being affected by crosstalk, thereby making it possible to sufficiently correct the north-south pincushion distortion.
The correction circuit may output the correction signal by a combination of a parabolic waveform changing in the horizontal scanning period and another function waveform.
In this case, the higher-order distortion component generated in the north-south pincushion distortion can be corrected by the combination of the parabolic waveform and another function waveform. Even when the deflection angle is large, therefore, the gull-wing distortion is prevented from being generated without being affected by the crosstalk, thereby making it possible to sufficiently correct the north-south pincushion distortion.
The vertical deflection apparatus may further comprise a plurality of pulse generation circuits that respectively generate pulse signals in the horizontal scanning period, and a synthesizer that synthesizes the pulse signals respectively generated by the plurality of pulse generation circuits with the correction signal output from the correction circuit. The superimposition device may superimpose a correction current based on an output signal of the synthesizer on the vertical deflection current.
In this case, a pulse component corresponding to the pulse signal in the correction current superimposed on the vertical deflection current is integrated by the vertical deflection coil. Consequently, the higher-order distortion component generated in the north-south pincushion distortion is corrected by the integrated pulse component. Even when the deflection angle is large, therefore, the gull-wing distortion is prevented from being generated without being affected by the crosstalk, thereby making it possible to sufficiently correct the north-south pincushion distortion.
The vertical deflection apparatus may further comprise a blanking circuit that sets the correction current to zero in a vertical blanking interval.
In this case, the correction current becomes zero in the vertical blanking interval, thereby achieving power saving.
A vertical deflection apparatus according to still another aspect of the present invention is a vertical deflection apparatus for supplying a vertical deflection current to a vertical deflection coil to deflect an electron beam in the vertical direction of a screen, which comprises a vertical deflection current output circuit that outputs the vertical deflection current to the vertical deflection coil; a correction circuit that outputs a correction signal periodically changing in a parabolic shape in a horizontal scanning period to correct a north-south pincushion distortion; and a superimposition device that superimposes a correction current based on the correction signal output from the correction circuit on the vertical deflection current, the correction circuit outputting the correction signal by a combination of a parabolic waveform changing in the horizontal scanning period and another function waveform.
In the vertical deflection apparatus according to the present invention, the vertical deflection current is output to the vertical deflection coil by the vertical deflection current output circuit. The correction signal changing in a parabolic shape in the horizontal scanning period is output to correct a north-south pincushion distortion by the correction circuit. Further, the correction current based on the correction signal output from the correction circuit is superimposed on the vertical deflection current by the superimposition device.
In this case, a higher-order distortion component generated in the north-south pincushion distortion can be corrected by the combination of the parabolic waveform and another function waveform. Even when the deflection angle is large, therefore, the gull-wing distortion is prevented from being generated without being affected by crosstalk, thereby making it possible to sufficiently correct the north-south pincushion distortion.
Another function waveform may be an n-th power waveform, where the n may be a real number.
In this case, the higher-order distortion component generated in the north-south pincushion distortion can be corrected by the combination of the parabolic waveform and the n-th power waveform.
The correction circuit may output the correction signal on the basis of a function expressed by the following equation (1), where n1, n2, . . . , nk may be respectively positive real numbers, and An1, An1, . . . , Ank may be respectively coefficients:
Y=An1Xn1+An2Xn2+ . . . +AnkXnkxe2x80x83xe2x80x83(1)
In this case, the higher-order distortion component generated in the north-south pincushion distortion can be corrected by arbitrarily setting the coefficients An1, An2, . . . , Ank.
The another function waveform may be a sine waveform.
In this case, the higher-order distortion component generated in the north-south pincushion distortion can be corrected by the combination of the parabolic waveform and the sine waveform.
The sine waveform may have a period which is a/b times the horizontal scanning period and have a variable phase, where the a and b may be integers.
In this case, the higher-order distortion component generated in the north-south pincushion distortion can be corrected by arbitrarily setting the coefficient a, the coefficient b, and the phase, respectively.
The vertical deflection apparatus may further comprise a blanking circuit for setting the correction current to zero in a vertical blanking interval.
In this case, the correction current becomes zero in the vertical blanking interval, thereby achieving power saving.
A vertical deflection apparatus according to a further aspect of the present invention is a vertical deflection apparatus for supplying a vertical deflection current to a vertical deflection coil to deflect an electron beam in the vertical direction of a screen, which comprises a vertical deflection current output circuit that outputs the vertical deflection current to the vertical deflection coil; a correction circuit that outputs a correction signal for correcting a north-south pincushion distortion; a plurality of pulse generation circuits that respectively generate pulse signals in a horizontal scanning period; a synthesizer that synthesizes the pulse signals respectively generated by the plurality of pulse generation circuits with the correction signal output from the correction circuit; and a superimposition device that superimposes a correction current based on an output signal of the synthesizer on the vertical deflection current.
In the vertical deflection apparatus according to the present invention, the vertical deflection current is output to the vertical deflection coil by the vertical deflection current output circuit. The correction signal for correcting a north-south pincushion distortion is output from the correction circuit. Further, the pulse signals are respectively generated in the horizontal scanning period by the plurality of pulse generation circuits. The pulse signals respectively generated by the plurality of pulse generation circuits are synthesized with the correction signal output from the correction circuit by the synthesizer. The correction current based on the output signal of the synthesizer is superimposed on the vertical deflection current by the superimposition device.
In this case, a pulse component corresponding to the pulse signal in the correction current superimposed on the vertical deflection current is integrated by the vertical deflection coil. Consequently, a higher-order distortion component generated in the north-south pincushion distortion is corrected by the integrated pulse component. Even when the deflection angle is large, therefore, a gull-wing distortion is prevented from being generated, thereby making it possible to sufficiently correct the north-south pincushion distortion.
The superimposition device may comprise a transformer having a primary winding and a secondary winding, and a drive circuit connected to the primary winding of the transformer, the secondary winding of the transformer may be connected in series with the vertical deflection coil, and the drive circuit may supply a drive current to the primary winding of the transformer in response to the output signal of the synthesizer.
In this case, the drive current is supplied to the primary winding of the transformer is response to the output signal of the synthesizer by the drive circuit. Consequently, the correction current based on the output signal of the synthesizer is superimposed on the vertical deflection current. The correction current can be easily superimposed on the vertical deflection current.
The vertical deflection apparatus may be so constructed that the plurality of pulse generation circuits can respectively control the pulse height values of the pulse signals independently.
Consequently, higher-order distortion components of various sizes in the north-south pincushion distortion can be corrected.
The vertical deflection apparatus may be so constructed that the plurality of pulse generation circuits can respectively control the phases or the pulse widths of the pulse signals independently.
Consequently, higher-order distortion components having various phases or widths in the north-south pincushion distortion can be corrected.
The vertical deflection apparatus may be so constructed that the plurality of pulse generation circuits can respectively control the polarities of the pulse signals independently.
Consequently, higher-order distortion components having various polarities in the north-south pincushion distortion can be corrected.
The vertical deflection apparatus may further comprise a first modulation circuit that modulates the pulse height value of the correction signal output from the correction circuit in a vertical scanning period, and a second modulation circuit that modulates the pulse height values of the pulse signals respectively output from the plurality of pulse signal generation circuits in the vertical scanning period.
In this case, the pulse height value of the correction signal output from the correction circuit is modulated in the vertical scanning period by the first modulation circuit, and the pulse height values of the pulse signals respectively output from the plurality of pulse signal generation circuits are modulated in the vertical scanning period by the second modulation circuit. Consequently, it is possible to correct a suitable amount of correction in each of portions on the screen.
The synthesizer may comprise an adder that adds the pulse signals respectively generated by the plurality of pulse generation circuits to the correction signal output from the correction circuit.
In this case, the correction signal output from the correction circuit and the pulse signals respectively generated by the plurality of pulse signal generation circuits are added together by the adder, so that the pulse signals and the correction signal are synthesized.
The vertical deflection apparatus may further comprise a blanking circuit that sets the correction current to zero in a vertical blanking interval.
In this case, the correction current becomes zero in the vertical blanking interval, thereby achieving power saving.